Hearing aid



FIG. 1 is a perspective view of a hearing aid as seen from the top and right side;

FIG. 2 is top view thereof;

FIG. 3 is a right side view thereof;

FIG. 4 is a bottom view thereof;

FIG. 5 is a left side view thereof;

FIG. 6 is a front view thereof; and,

FIG. 7 is a rear view thereof.

The broken lines illustrate portions of the hearing aid that form no part of the claimed design. 

CLAIM The ornamental design for a hearing aid, as shown and described. 